In the field of non-impact printing, the most common types of printers have been the thermal printer and the ink jet printer. When the performance of a non-impact printer is compared with that of an impact printer, one of the problems in the non-impact machine has been the control of the printing operation. As is well-known, the impact operation depends upon the movement of impact members such as wires or the like and which are typically moved by means of an electromechanical system which may, in certain applications, enable a more precise control of the impact members.
The advent of non-impact printing as in the case of thermal printing, brought out the fact that the heating cycle must be controlled in a manner to obtain maximum repeated operations. Likewise, the control of ink jet printing in at least one form thereof must deal with rapid starting and stopping movement of the ink fluid from a supply of the fluid. In each case, the precise control of the thermal elements and of the ink droplets is necessary to provide for both correct and high speed printing.
In the matter of ink jet printing, it is extremely important that the control of the ink droplets be precise and accurate from the time of formation of the droplets to depositing of such droplets on paper or like record media and to make certain that a clean printed character results from the ink droplets. While the method of printing with ink droplets may be performed either in a continuous manner or in a demand pulse manner, the latter type method and operation is disclosed and is preferred in the present application as applying the features of the present invention. The drive means for the ink droplets is generally in the form of a crystal or piezoelectric type element to provide the high speed operation for ejecting the ink through the nozzle while allowing time between droplets for proper operation. The ink nozzle construction must be of a nature to permit fast and clean ejection of ink droplets from the print head.
In the ink jet printer, the print head structure may be a multiple nozzle type with the nozzles aligned in a vertical line and supported on a print head carriage which is caused to be moved or driven in a horizontal direction for printing in line manner. The ink droplet drive elements or transducers may be positioned in a circular configuration with passageways leading to the nozzles. Alternatively, the printer structure may include a plurality of equally-spaced horizontally-aligned single nozzle print heads which are caused to be moved in back-and-forth manner to print successive lines of dots making up the lines of characters. In this latter arrangement, the drive elements or transducers are individually supported along a line of printing.
In the concept of dot matrix printing, it is generally desired to place the print element actuators in a position to allow characters to be printed in serial manner and this placement requires that the print wires, nozzles, electrodes or other like print actuators be very closely spaced with respect to each other. Since the print actuators are generally larger in size than the diameter of the printed dot, a relatively long wire, channel or like element must be provided to bring the desired print activity from its source, such as a moving armature or plunger or a pressure generating piezoelectric crystal to a vertical closely-spaced column arranged in a pattern such that a column of closely-spaced tangentially coincident or overlapping dots will be produced on the record media if all actuators are fired or actuated at one time. However, it is likely seen that the use of long wires or channels are known to lower the performance of the actuators.
Since it is desirable to eliminate the long curving transition section between the drive elements and the nozzles as in the case of the circular arrangement mentioned above, it is proposed to provide an array of ink jet transducers in a spaced configuration or manner for use in a compact print head.
Representative prior art in the field of ink jet print heads includes U.S. Pat. No. 3,373,437, issued to R. G. Sweet et al. on Mar. 12, 1968, which discloses a fluid droplet recorder with a plurality of jets and wherein a common fluid system supplies ink to an array of side-by-side nozzles.
U.S. Pat. No. 3,683,212 issued to S. I. Zoltan on Aug. 8, 1972, discloses an electro acoustic transducer coupled to liquid in a conduit which terminates in a small orifice through which droplets of ink are ejected.
U.S. Pat. No. 3,832,579 issued to J. P. Arndt on Aug. 27, 1974, discloses a pulsed droplet ejecting system wherein a liquid carrying conduit includes a portion capable of conducting pressure waves in the liquid by means of an electro acoustic transducer surrounding the conduit portion and causing ejection of droplets from the nozzle.
U.S. Pat. No. 3,988,745 issued to S. B. Sultan on Oct. 26, 1976 discloses an ink jet printer having opposed plates provided with piezoelectric disks arranged in a coplanar pattern and a plurality of nozzles arranged in generally linear manner.
U.S. Pat. No. 4,005,440 issued to J. R. Amberntsson et al. on Jan. 25, 1977 discloses a printing head of smaller size and wherein the openings of the capillary tubes are located closer to one another.
U.S. Pat. No. 4,014,029 issued to R. Lane et al. on Mar. 22, 1977 discloses a nozzle plate having at least two rows of nozzles and effecting a staggered nozzle array wherein the nozzles in one row are laterally displaced with respect to the nozzles in another row to print a portion of a line at a time, a line at a time, or several lines at a time.
U.S. Pat. No. 4,023,180 issued to W. J. Zenner on May 10, 1977 discloses a dot printer with electrically propelled ink wherein current is passed through the ink under the influence of a magnetic field between electrodes and the resulting EMF propels droplets of ink through nozzles arranged in linear manner.
U.S. Pat. No. 4,038,667 issued to S. L. Hou et al. on July 26, 1977, discloses a plurality of droplet-forming nozzles arranged in linear manner and wherein droplets are ejected by means of piezoelectric transducers surrounding the nozzles.
U.S. Pat. No. 4,128,345 issued to J. F. Brady on Dec. 5, 1978 discloses a fluid impulse matrix printer having a two-dimensional array of tubes in a dot matrix for printing a complete character at a time.
U.S. Pat. No. 4,158,847 issued to J. Heinzl et al. on June 19, 1979, discloses a piezoelectric operated print head having twin columns of six nozzles.
And, U.S. Pat. No. 4,189,734 issued to E. L. Kyser et al. on Feb. 19, 1980 discloses a writing fluid source feeding drop projection means which ejects a series of droplets through a column of seven nozzles with sufficient velocity to traverse a substantially straight trajectory to the recording medium.